iPhone 12 button hardware or software issue

Hi, my new iPhone 12 when restarts goes directly into silent mode. The silent button does not respond at all . Assistive touch can be used to turn on the ringer but the button just doesn’t work. Several time restarted the phone settings but issue is persistent. When ringer is turned on and phone is restarted it goes back to silent mode on default. Is this a hardware issue or software?